This invention relates to radiation transmission systems which permit radiation, particularly infrared (IR) radiation, to be used in conveying information, such as spectral scanning information obtained by means of Fourier Transform spectroscopy, over relatively long distances and to various alternatively available accessory devices, or sample chambers.
In a recently filed application of one of the present inventors (Ser. No. 895,211, filed Aug. 11, 1986) a multi-unit spectrometer system is disclosed which permits a plurality of accessory units to be simultaneously connected to a single interferometer/detector unit.
The key concept of that system is the combining of confocal and collimated optical segments in an appropriate way to substantially eliminate vignetting (i.e., the loss of energy due to beam growth and the resultant loss of throughput). The use of confocal segments provides pairs of conjugate images, i.e., images in which all of the same rays are present in a matched relationship with respect to angle and location. By the proper arrangement of the optical elements in the system, the limiting aperture of the system can be reimaged at appropriate points in the system. As a result, the inherent spread of the beam is minimized, allowing the maximum possible signal to reach the detector.